This invention relates to heating of water by solar radiation. More particularly, the present invention relates to passive solar heating of the water contained in a tank of water by use of substantially planar light absorbent fabric strips positioned substantially vertically in spaced relationship in the water to be heated.
Heating of water by means of electricity or gas is well known and effective, but it has become costly. Passive solar heating of water has been investigated as an alternative and/or supplement to conventional heating methods.
Various solar radiation collector designs have been suggested. Several of these designs seek to maximize absorption of solar radiation by focussing or concentrating sunlight upon a relatively small surface area by means of non-planar reflecting surfaces. T. Hopper, "Solar Energy Collecting Apparatus," U.S. Pat. No. 4,340,034 (July 20, 1982) discloses a plurality of elongated trough-like reflecting surfaces for concentrating solar energy onto a plurality of elongated focal regions through which water to be heated may be pumped. The present invention may be classified as a planar solar energy collecting apparatus and method rather than a concentrating solar energy collecting apparatus and method.
It is believed that the present invention will find its greatest application in the field of swimming pools. The use and enjoyment of recreational outdoor swimming pools can be increased by heating the water to a more comfortable temperature than the ambient temperature. This is especially true in the northern areas of the country where the summer season is relatively short and sufficiently warm days for swimming are limited.
Various designs of swimming pool covers have been proposed ( to maximize heating of water by sunlight and minimize loss of heat by reflection or re-radiation. For example, J. Trihey, "Solar Heating Apparatus For Swimming Pools," U.S. Pat. No. 4,313,421 (Feb. 2, 1982) discloses a flexible, inflatable pool cover comprising two sheets in which air may be forced to provide an insulating layer for insulating the pool during times when the sun is not shining. When the sun is shining, the air may be withdrawn from the cover, thereby allowing a substantial portion of the top sheet to bear against the bottom sheet and providing relatively good thermal conduction from the top sheet, warmed by the sun, to the pool surface. The device includes a hose or conduit having holes along its length to allow circulation of water in the pool to avoid a buildup of a hot layer at the pool surface by connecting said hose or conduit to the water outlet from a conventional pool filter. A plurality of drainage holes are provided in the pool cover to allow rainwater to enter the pool rather than being collected on top of the pool cover. K. Zook, "Flotable Pool Cover," U.S. Pat. No. 4,385,407 (May 31, 1983) claims a generally rectangular flexible sheet having the shape of the pool to be covered with a first substantially rigid floatable means attached to one edge of the cover and a second substantially rigid floatable means attached to the opposite edge of the cover, such that the flexible sheet and the first and second substantially rigid floatable means are adapted to float on the water's surface when a pool is to be covered by the pool cover, and adapted to be wound upon a roll when the pool is to be uncovered.
Solar heating apparatus have been proposed which employ solar heating collection means remote from the pool water itself. R. Garnett, "Solar Energy Collector," U.S. Pat. No. 3,200,820 (Aug. 17, 1965) discloses a non-planar parabolic solar energy collector for heating of swimming pool water. The efficiency of the apparatus is increased by re-reflectance of reflected sunlight back into the solar energy collector. M. Domenach, "Solar Swimming Pool Water Heater," U.S. Pat. No. 4,312,323 (Jan. 26, 1982) discloses a solar heating apparatus comprising an array of adjacent and substantially concentric annular flexible synthetic resin tubes surrounding the pool to be heated, said tubes having a rectified length equal to at least thirty times its horizontal cross-sectional width, having adjacent feed and return ends, a feed manifold connected to all of said feed ends, a return manifold connected to all of said return ends whereby the tubes are connected in parallel between the feed and return manifold. In operation, water from the pool is pumped through the inlet manifold into the tubes, heated by sunlight, and returned to the pool through the outlet manifold. R. Miller, "Solar Collector," U.S. Pat. No. 4,385,624 (May 31, 1983) discloses a solar heating apparatus similar to the apparatus disclosed in U.S. Pat. No. 4,312,323, in which pool water is pumped through at least one spiral hose mounted upon a cone shaped supporting surface whereby the water to be heated is pumped through an inlet which is adjacent the lowermost edge of the supporting surface so that the water is always pumped upwardly to the outlet end of the hose lines adjacent the apex of the cone shaped supporting surface. K. Kohl, "Low Cost, Low Pressure Solar Heated Fence Surrounding A Swimming Pool," U.S. Pat. No. 4,381,763 (May 3, 1983) discloses a remote solar heating apparatus incorporated into a panel fence surrounding the pool to be heated. These designs all have several disadvantages, including electrical energy consumption for pumping the pool water through the apparatus and permanent hardware in the pool area.
An in-pool solar heating apparatus is disclosed in R. Kremen, "Apparatus For Heating A Swimming Pool," U.S. Pat. No. 4,402,305 (Sept. 6, 1983). The heating apparatus comprises at least one reinforced, highly absorptive fabric liner which is ( preferably suspended in the pool water at or near the bottom of the pool in a substantially horizontal position. The fabric liner is preferably constructed of a carbon black ethylene-propylene rubber material, and is designed to be wound upon a storage spool when not in use.